Sure. What I meant was something you'd reasonably put in a tower. You could put it in a tower, but you'd have tons of empty space, as you don't have enough PCI-E lanes for any slots beyond the GPUs. Apple could have maybe done PCI-E GPUs, but we've beaten that discussion to death. It would have required all the breakout wires, which would have given Ive a stroke.
(I'm not endorsing what Apple did with the PCI-E GPUs. But I get their motivations for doing so.)
So, imagine a world where they put some low dollar something like a GT640 on the logic board to create the video output portion of TB. All of the TB hurdles chucked out the window for $50 (Apple's cost)
Enough with trying to find reasons for something that has no particular good reason. Apple could easily have created a machine with TB and PCIE slots. They didn't want to. They have exited the "serious" market and are working their way downhill into "prosumer".
When a prosumer gets red banding in a wedding video, he shrugs. When a DP looking at dailies for Terminator 12 sees red banding he cries foul and lambastes Apple in all the forums. So, keep 2,000,000 prosumers happy (and paying) or play with the big boys?
Apple got a look at real cash with iPod/iPad/iPhone and hasn't looked back.
I would never expect a serious machine from Apple again, whether it be in 2015 or 2020. Prosumer (emphasis on "sumer" as in "paying") is the market and they want shiny with Twitter integration.
A Dual Xeon machine could have had 6 TB ports and plenty of slots for all. It would have been the best machine on the planet and Apple went for ...the middle.
And by the way, stop with the "Only way to have 6TB ports" stuff. For fun, go look through posts before June 2013. Find me someone demanding 6 TB ports . People mentioned that they hoped there would be TB ports, mainly as a way of joining the TB ecosystem, ability to access same drive as rMBP from the field, etc. But nobody, and I mean NOBODY ever said "It had better have 6 TB ports or I'm not buying it". They also never said "It had better take up 1/8 the space or I'm not buying it."
As has been pointed out exactly 1 gazillion times before, this (nMP) was the answer to a question that nobody (outside Apple) had asked.
When will it be updated? When it is cheapest & easiest for Apple to do so. When they run out of the CPUs or AMD stops making the 3+ year old GPUs, etc. It will get 10% faster, be slightly skinnier, and have better Twitter integration. (Maybe a dedicated twitter button, right by the glowing power switch)